There has been a wireless electronics revolution in recent years due to the rapid advancements and adoption of many new digital wireless communication protocols. For example, Code Division Multiple Access (CDMA) and Global System for Mobile communication (GSM) have greatly increased the popularity of digital cellular telephones, Wi-Fi local area network (LAN) protocols (such as 802.11b, 802.11g, 802.11a, etc.) have revolutionized wireless computer networks, and Bluetooth has provided a very useful short range wireless digital protocol for many different digital devices.
Although these new digital wireless protocols are designed to be resistant to errors, digital wireless communication is always subject to information loss due to various physical effects on the wireless signals. For example, radio interference, errors caused by multi-path reflections, radio signal shielding, range limitations, and other problems can degrade transmitted wireless signals such that information becomes lost.
Non real-time communication applications that use digital wireless protocols can easily handle the loss of information due to any of these reasons by simply requesting the retransmission of the lost information. However, real-time communication applications need to be robust enough to handle the occasional loss or corruption of information that is transmitted across a digital wireless channel.
One specific real-time communication application is the reception and immediate display of digital video information transmitted across a wireless digital communication channel. When some information is lost during the transmission of the digital video, there is not enough time to request and receive a retransmission of the lost information since retransmission brings significant delay which is not suitable for real-time applications such as video telephony and video streaming. Thus, when digital video information is lost, the digital video receiver must attempt to display one ore more video frames using the received incomplete digital video information.
Several different techniques have been developed for decoding and displaying digital video frames as best as possible despite the loss of some digital video information. These techniques developed for displaying incomplete digital video information in the best possible manner are generally referred to as Error Concealment (EC) techniques since these techniques attempt to conceal the lack of accurate video information caused by errors.
The existing techniques of digital video Error Concealment (EC) mainly fall into the following two categories: Temporal Error Concealment (TEC) and Spatial Error Concealment (SEC). Temporal Error Concealment (TEC) exploits temporal correlation between nearby (in a time dimension) video frames. TEC conceals errors by replacing corrupt macroblocks (MBs) with the processed macroblocks from previously reconstructed video frames. On the other hand, Spatial Error Concealment (SEC) exploits spatial correlation within a single video frame. Spatial Error Concealment conceals errors by predicting the erroneous pixels from neighboring pixels (or transform coefficients).
Block Replacement Error Concealment (BREC) is the simplest and the most straightforward type of Temporal Error Concealment (TEC). Block replacement error concealment conceals errors by replacing erroneous macroblocks with the co-located macroblocks from a previously reconstructed video frame. This simple approach to temporal error concealment assumes a zero motion vector for the erroneous macroblocks to be concealed. The performance may be improved by utilizing more accurate motion vectors rather than a zero motion vector. Motion Vector Processing (MVP) is such an example.
A very simple Spatial Error Concealment (SEC) implementation may just replace erroneous pixels with information from the nearest available pixels. Improvement can be achieved by utilizing interpolation and spatial prediction. The Spatial Error Concealment (SEC) may be performed either in the pixel domain or in the frequency domain.
In order to provide the best looking video to user when errors in the communication stream occur, the digital video receiver should select the optimum error concealment system. Thus, it would be desirable to create digital video receivers that carefully select the best error concealment system and then implement the error concealment systems in manners that display the best possible video image from the incomplete digital video information.